Many processes and coatings have been developed for protecting metal substrates, and particularly plain carbon steel substrates, from direct and electrochemical corrosion. Previously, metal substrates have been protected in varying degrees by applying organic and metal coatings such as phosphate, paint, plastic resins, zinc, lead, stainless steel, aluminum and the like.
Geeck U.S. Pat. No. 4,391,855 discloses an effective corrosion resistant coating for a metal substrate. This coating has a corrosion inhibiting finely powdered metal dispersed in a phenoxy resin organic bonding material and solvents. In this coating powdered zinc, cadmium, stainless steel and aluminum are all suitable corrosion inhibitors, although zinc is preferred for steel substrates.
Corrosion resistant coatings are used in a variety of applications. Most applications require additional die drawing compounds applied over the coated metal substrate when it is to be cold drawn into different shapes for the purpose of not only permitting the drawing operation, but also for preventing the destruction of the coating film.
Various drawing agents have also been mixed with liquid paint applied to metal substrates to increase its drawability so that usually limited or sometimes even no additional die drawing compound is required to be applied over the paint to permit a drawing operation which is not deep or severe. However, the addition of such agents to a coating having a powdered metal for inhibiting corrosion, such as the coating of U.S. Pat. No. 4,391,855, renders ineffective or greatly retards and usually destroys its corrosion inhibiting properties.